The present invention relates generally to fluid flow deflector apparatus and in particular to such deflector apparatus employing a helical or other spiral shaped deflector member to provide more fluid turbulence and reduce laminar fluid flow while producing less resistence to flow and less pressure drop than other deflectors thereby resulting in a more efficient operation.
The fluid flow deflector apparatus of the present invention is especially useful when employed as a heating fluid deflector in a sheet dryer apparatus including a wood veneer dryer, a gypsum wallboard dryer, or insulation board dryer, where it extends substantially perpendicular to the flow of the stream of heating fluid, such as hot air or steam, and deflects such stream upward and downward into contact with separated sheets being dried. This results in better mixing of the heating fluid as well as a higher and more uniform temperature of the portion of such fluid which contacts the sheet material, thereby resulting in a more efficient drying operation. However, the fluid flow deflector apparatus is also useful in heat exchanger apparatus where the axis of the deflector member extends substantially parallel to the direction of fluid flow and such deflector is located either inside or outside a conduit in heat exchanging relationship with another fluid to provide for a more efficient heat exchanger operation. The term "fluid" as used herein refers not only to liquids and gases, but also solid particulate material which flows, such as gypsum powder used to make wallboard.
Previously it has been proposed in my earlier U.S. Pat. No. 4,121,350 of A. Buchholz, issued Oct. 24, 1978 to provide a sheet dryer apparatus using deflector members as flat baffles of rectangular or V-shaped cross-section to deflect the stream of drying fluid such as hot air or steam into contact with the wood veneer or other sheet material being dried for more efficient drying. However, these deflector members provide a high resistence to airflow which increases the pressure drop and reduces airflow within the dryer sections. In addition, they do not deflect the drying fluid in a sideways direction. As a result, there is some laminar airflow and the drying fluid is not mixed as completely so that the temperature of the fluid which contacts the top and bottom of the sheet material is not sufficiently high or uniform throughout the dryer. Thus, a laminar flow of higher temperature air tends to exist in the intermediate region between the sheets while the air which contacts the sheets is of lower temperature and is not very uniform. These problems are overcome using the helical deflector member of the present invention which has a low resistence to airflow and produces little pressure drop as well as more turbulence to eliminate laminar airflow. As a result, there is better mixing of the airflow from side-to-side or top-to-bottom in the space between two adjacent separated sheets being dried and better mixing from deck-to-deck. Thus, the sheet material on the top deck is dried more nearly at the same temperature and moisture content as the sheet material on the bottom deck of the dryer.
In addition, the fluid flow deflector of the invention has other advantages when used in heat exchanger apparatus. Thus, the deflector may be supported within a conduit transmitting heating fluid so that the deflector member is positioned with its axis extending substantially parallel to the direction of fluid flow. When so positioned, the deflector member deflects the stream of hot gas or other heating fluid outwardly into contact with the inner surface of the conduit, which conducts the heat to a surrounding fluid outside of the conduit. The helical deflector member produces greater turbulence, prevents laminar fluid flow and provides a more uniform temperature in the fluid along the surface of the conduit without greatly increasing the resistence to fluid flow within the conduit. Thus, it prevents laminar airflow which tends to cause higher temperature air to flow down the center of the conduit away from its inner surface. In another embodiment the helical deflector member itself may be used as a heat exchanger element such as by welding such deflector member to the outside surface of a conduit, such as a steam pipe, conveying heating fluid for heating the surrounding air or other fluid flowing past the outer surface of such conduit and into contact with such deflector members. In addition, solid particulate fluid material, such as gypsum powder, can be caused to flow over the surfaces of such external deflector members operating as heat exchangers welded to the outside of the conduit through which the heating fluid is supplied, for more efficient drying of such particulate material.